1. Field of the Invention
The present invention relates to a keyboard apparatus having a frame integrally formed by resin and pivotably supporting a plurality of keys, and more particularly, to a keyboard apparatus having hammers supported on a frame so as to each pivot in conjunction with a corresponding key and impart inertia to the key.
2. Description of the Related Art
Conventionally, keyboard apparatuses have been known in which a frame integrally formed by resin and pivotably supporting a plurality of keys is adapted to be supported on a musical instrument main body. Among these, some keyboard apparatus includes hammers supported on the frame and each adapted to pivot in conjunction with a corresponding key and impart inertia to a pivotal motion of the key (Japanese Patent Publication No. 3819136 and Japanese Laid-open Patent Publication No. 9-244623).
In the keyboard apparatuses disclosed in Japanese Patent Publication No. 3819136 and Japanese Laid-open Patent Publication No. 9-244623, the frame is supported at its contact portions on, e.g., a keybed, which is a part of the musical instrument main body. Relatively large loads are applied to key supports and hammer supports that pivotally support keys and hammers, respectively. Since these loads are applied via the key supports and the hammer supports to the contact portions where the frame contacts the musical instrument main body, ribs or other thickened portions are usually formed at or between the key supports, the hammer supports, and the contact portions of the frame.
In these keyboard apparatuses, an initial stopper adapted for contact with the hammers to thereby restrict key-depression initial positions of the keys in a key depression forward stroke is provided on the frame, and key guides for guiding pivotal motions of the keys are also provided on the frame.
In such a keyboard apparatus, it is necessary to appropriately lay out, on the frame, parts applied with large loads and the contact portions. Otherwise, the reinforcement resin is wastefully used, resulting in increased weight and cost.
With the construction disclosed in Japanese Patent Publication No. 3819136, since the frame is configured to be in contact at a broad longitudinal area with the musical instrument main body, a large amount of resin is used and there is wastage of resin from the viewpoint of withstanding the loads.
In the apparatuses disclosed in Japanese Patent Publication No. 3819136 and Japanese Laid-open Patent Publication No. 9-244623, since the frame has thickened portions at locations forward and downward of the hammer supports, there is scope for a reduction of the amount of resin. In addition, the frame is designed to give a thick feel as seen from front, and there is thus scope for improvement of the degree of freedom of design.